The role of the respiratory and laryngeal systems in the generation and regulation of aerodynamic characteristics of speech in individuals with and without cleft palate will be explored in three related studies. The specific aims include the determination of (i) lung volume levels used to initiate and terminate speech production, (ii) the limits of the respiratory system to respond to sudden venting of intraoral air pressure during production of bilabial stop consonants, and (iii) the possible role of respiratory and laryngeal reflexes in the regulation of oral air pressure. The three studies are linked theoretically to the hypothesis that speakers employ both volitional and non-volitional strategies to regulate the aerodynamic substrates of speech production. The first study will determine respiratory lung volume levels of children with cleft palate and various degrees of oral-nasal coupling as compared to control speakers. This study will directly test the hypothesis that children with velopharyngeal inadequacy (VPI) use increased respiratory effort as a compensatory strategy. Relationships among variables such as lung volume levels, speaking intensity, and nasal air emission will be determined. The second study will discern the limits of the respiratory system in maintaining adequate oral air pressures in response to sudden and unexpected pressure venting in speakers both with and without cleft palate. A newly developed valve will be employed to precisely control the magnitude and timing of pressure perturbations. The rate and maximum levels of pressure recovery following perturbation will be examined relative to cleft status, age, and lung volume levels of the speakers. The third study will attempt to elicit laryngeal reflexes from non-cleft speakers in response to pressure venting. The methodology of the second study will be combined with electromyographic (EMG) recordings from the levator veli palatini (LVP) and posterior cricoarytenoid (PCA) muscles. Anticipated changes in PCA and/or LVP activity in response to pressure venting will be interpreted relative to theories of pressure regulation. These studies are a logical extension of the Principal Investigator's First Award (R29-DE10175). The proposed studies are expected to provide new insights into the respiratory and laryngeal motor control strategies employed by speakers both with and without cleft palate. The information obtained from these studies will be instrumental in defining normal aspects of speech aerodynamics. In addition, this information may facilitate the diagnosis and management of individuals with VPI. It is possible, for example, that therapeutic techniques may be developed that incorporate specific respiratory strategies employed by speakers with cleft palate who exhibit acceptable speech characteristics.